[PATCH AUTOSEL 6.11 078/244] x86/bugs: Fix handling when SRSO mitigation is disabled

Sasha Levin
2024-09-25T11:39:48Z

From: David Kaplan <david.kaplan@amd.com>

[ Upstream commit 1dbb6b1495d472806fef1f4c94f5b3e4c89a3c1d ]

When the SRSO mitigation is disabled, either via mitigations=off or
spec_rstack_overflow=off, the warning about the lack of IBPB-enhancing
microcode is printed anyway.

This is unnecessary since the user has turned off the mitigation.

[ bp: Massage, drop SBPB rationale as it doesn't matter because when
mitigations are disabled x86_pred_cmd is not being used anyway. ]

Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/20240904150711.193022-1-david.kaplan@amd.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/kernel/cpu/bugs.c | 14 +++++---------
1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 45675da354f33..468449f73a957 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2551,10 +2551,9 @@ static void __init srso_select_mitigation(void)
{
bool has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE);

- if (cpu_mitigations_off())
- return;
-
- if (!boot_cpu_has_bug(X86_BUG_SRSO)) {
+ if (!boot_cpu_has_bug(X86_BUG_SRSO) ||
+ cpu_mitigations_off() ||
+ srso_cmd == SRSO_CMD_OFF) {
if (boot_cpu_has(X86_FEATURE_SBPB))
x86_pred_cmd = PRED_CMD_SBPB;
return;
@@ -2585,11 +2584,6 @@ static void __init srso_select_mitigation(void)
}

switch (srso_cmd) {
- case SRSO_CMD_OFF:
- if (boot_cpu_has(X86_FEATURE_SBPB))
- x86_pred_cmd = PRED_CMD_SBPB;
- return;
-
case SRSO_CMD_MICROCODE:
if (has_microcode) {
srso_mitigation = SRSO_MITIGATION_MICROCODE;
@@ -2643,6 +2637,8 @@ static void __init srso_select_mitigation(void)
pr_err("WARNING: kernel not compiled with MITIGATION_SRSO.\n");
}
break;
+ default:
+ break;
}

out:
--
2.43.0